The present invention relates to a constant velocity ball joint permitting axial displacement.
The most frequent type of plunging joints are so-called VL joints (cross-groove joints) such as according to U.S. Pat. No. 4,678,453 wherein the center lines of the outer tracks and of the inner tracks each form oppositely directed angles of intersection with the longitudinal joint axis and are positioned in planes extending parallel to the longitudinal joint axis or on a cylindrical face around the longitudinal joint axis.
From U.S. Pat. No. 3,133,431, there are known plunging joints wherein the center lines of the outer tracks and of the inner tracks form identically sized angles of intersection with the longitudinal joint axis, i.e., they are positioned in planes which contain the longitudinal joint axis itself.
Both the above-mentioned types of joint are joints with straight tracks.
It would be desirable to provide a new type of plunging joint for large articulation angles and relatively short displacement paths.
The present invention provides a constant velocity ball joint in the form of a counter track joint. The joint includes an outer joint part with outer tracks, an inner joint part with inner tracks, torque transmitting balls which are received in pairs of tracks consisting of outer tracks and inner tracks which are curved outwardly with reference to the longitudinal joint axis A, and a ball cage with cage windows in which the balls are held in a common plane and are guided on to the angle-bisecting plane when the joint is articulated. First outer tracks, together with first inner tracks, form first pairs of tracks whose first control angles xcex21 open in a first axial direction and in which first balls are held. Second outer tracks, together with second inner tracks, form second pairs of tracks whose second control angles xcex22 open in a second axial direction and in which second balls are held. The control angles xcex21, xcex22 are defined as angles between tangential planes at the ball contact points in the tracks. Further, the outer joint part and the inner joint part are axially displaceable relative to one another and the first control angles xcex21 and the second control angles xcex22 change in opposite senses when a relative axial displacement occurs. The axial displacement path Vmax is limited to a maximum value that produces a minimum value of at least 8xc2x0 for the respective smaller control angles xcex21, xcex22. The present joint provides an axial displacement path having at least 0.8 mm, and preferably more than 1.0 mm of play. This is substantially above the axial play of fixed joints, which in comparison is at most 0.5 mm.
In one form of the displacement path, the joint In accordance with the invention provides a way to uncouple axial vibrations and thus contributes towards improving the noise, vibration, harshness (NVH) behavior. The present design is also advantageous in that it is possible to un-fine the surfaces during the machining operations. Also, the design of the tracks provides a joint with axial centering characteristics.
In particular, the tracks are curved as in Rzeppa joints or undercut-free (UF) joints. As a consequence, even with larger articulation angles, there is achieved adequate ball control due to sufficiently large control angles.
By limiting the axial displacement path, it is ensured that the control angles do not become too small as a result of the axial displacement. The stops for delimiting the axial plunging path can become effective exclusively between the outer joint part and the cage, or exclusively between the inner joint part and the cage, or between both pairs simultaneously; in each case when the joint is in the aligned position, in which case the longitudinal axes of the inner joint part and of the outer joint part coincide. As the ball cage is radially set free relative to the inner joint part and to the outer joint part, the joint is characterised by particularly low friction. Furthermore, because of the counter-track formation, it is ensured that the joint is axially self-centering and that the forces acting on the cage are kept within certain limits. In addition, the way in which the balls are enveloped by the tracks in a cross-sectional view is particularly advantageous.
Other advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.